The present invention relates to devices for precoating a filter media to allow for filtration of a liquid substance, more particularly, a filter aid dispensing arrangement where a filter aid, for example, diatomaceous earth, is placed in container means and a liquid substance is supplied to the container means to mix with the filter aid to form a precoat slurry and where the slurry is emitted through openings provided in the container means to deposit the precoat slurry on a filter medium.
Heretofore, the general procedure used in precoating the filter media required mixing filter aid and precoat liquid, for example by stirring in a separate container where the liquid may or may not be the substance to be filtered to form a precoat slurry which was then deposited on the filter media. In such methods it was very difficult to get a uniform precoat slurry so the filter aid was usually not deposited uniformly on the filter media. Accordingly in many instances it was necessary to provide other means to uniformly deposit the precoat on the filter media before filtration. In cases where the filter media is a thin substance, such as paper, and mechanical spreading is utilized the spreading action can tear the filter media.
Moreover, such methods are time consuming and require a laborer to stir the filter aid with a liquid substance to form the precoat slurry and still do not provide a uniform layer of filter aid deposited on the filter media. In some instances, the liquid substance mixed with the filter aid is very hot, such as cooking oil which is to be filtered before being reused. Also in previous arrangements no means are provided to accurately measure the amount of filter aid without transferring the filter media to the mixing device.